Remove propel/propel.php from signature file (#7098)

# Description & Issue number it closes 
Closes Issue 7097

## Screenshots (if appropriate)
N/A

## How to test the changes?
Verify propel/propel.php is not listed in the generated signatures.json
file

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update

# How Has This Been Tested?
Performed `npm run deploy` and verified resulting signatures.json file.

# Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

Gruntfile.js

@@ -416,6 +416,7 @@ module.exports = function (grunt) {
                             "!Images/Person/thumbnails/*.jpg",
                             "!composer.lock",
                             "!Include/Config.php",
+                            "!propel/propel.php",
                             "!integrityCheck.json",
                         ],
                         dest: "churchcrm/",